Our studies on oxygen toxicity in the red cell rely on the use of xenobiotic agents as biochemical probes. In our overall approach, we generally study the interaction of a xenobiotic agent with oxygen and with red cell components such as hemoglobin and we ultimately extend these studies to the red cell. Our experimental protocols are designed to answer questions of red cell function and toxicity. In this application we present experiments that continue our studies on changes in red cell structure and metabolic function mediated by xenobiotics that generate reduced products of oxygen metabolism and other reactive intermediates. In these studies we determine 1) alterations in membrane proteins as evaluated by sodium dodecyl sulfate polyacrylamide gel electrophoresis, immunoblot electrophoresis using antibodies raised to major membrane proteins and one dimensional peptide mapping, 2) alterations in membrane phospholipids as measured by two-dimensional thin layer chromatography and the use of fluorescent probes such as trinitrobenzene sulfonate and fluorescamine for evaluation of changes in membrane phospholipid organization 3) alterations in glucose metabolism. Recently we observed that a tryptophan metabolite, 3-hydroxyanthranilic acid undergoes base catalysed antoxidation to produce reduced products of oxygen-metabolism. We present experiments that address the molecular mechanism of the interaction of 3-hydroxyanthranilic acid and oxygen and also experiments on the effect of 3-hydroxyanthranilic acid in red cells. Our diversified approach has allowed us to develop model systems that contribute to our knowledge of oxygen cytotoxicity and has allowed the opportunity of probing red cell metabolism and structure with xenobiotics, to determine both the physiological function of the red cell and its behavior under conditions of mild oxidative stress.